diff --git a/src/calibre/ebooks/metadata/opf2.py b/src/calibre/ebooks/metadata/opf2.py
index 395fe0c484..fb80cc8bfe 100644
--- a/src/calibre/ebooks/metadata/opf2.py
+++ b/src/calibre/ebooks/metadata/opf2.py
@@ -21,7 +21,7 @@ from calibre.ebooks.metadata.book.base import Metadata
 from calibre.utils.date import parse_date, isoformat
 from calibre.utils.localization import get_lang, canonicalize_lang
 from calibre import prints, guess_type
-from calibre.utils.cleantext import clean_ascii_chars
+from calibre.utils.cleantext import clean_ascii_chars, clean_xml_chars
 from calibre.utils.config import tweaks
 
 class Resource(object):  # {{{
@@ -1436,7 +1436,10 @@ def metadata_to_opf(mi, as_string=True, default_lang=None):
             attrib['name'] = name
         if content:
             attrib['content'] = content
-        elem = metadata.makeelement(tag, attrib=attrib)
+        try:
+            elem = metadata.makeelement(tag, attrib=attrib)
+        except ValueError:
+            elem = metadata.makeelement(tag, attrib={k:clean_xml_chars(v) for k, v in attrib.iteritems()})
         elem.tail = '\n'+(' '*8)
         if text:
             try:
diff --git a/src/calibre/utils/cleantext.py b/src/calibre/utils/cleantext.py
index 219199815e..81614077bd 100644
--- a/src/calibre/utils/cleantext.py
+++ b/src/calibre/utils/cleantext.py
@@ -28,13 +28,14 @@ def clean_ascii_chars(txt, charlist=None):
         pat = re.compile(u'|'.join(map(unichr, charlist)))
     return pat.sub('', txt)
 
+def allowed(x):
+    x = ord(x)
+    return (x != 127 and (31 < x < 0xd7ff or x in (9, 10, 13))) or (0xe000 < x < 0xfffd) or (0x10000 < x < 0x10ffff)
+
 def clean_xml_chars(unicode_string):
-    def allowed(x):
-        x = ord(x)
-        return (0x0001 < x < 0xd7ff) or (0xe000 < x < 0xfffd) or (0x10000 < x < 0x10ffff)
     return u''.join(filter(allowed, unicode_string))
 
-##
+
 # Fredrik Lundh: http://effbot.org/zone/re-sub.htm#unescape-html
 # Removes HTML or XML character references and entities from a text string.
 #
@@ -60,6 +61,7 @@ def unescape(text, rm=False, rchar=u''):
             except KeyError:
                 pass
         if rm:
-            return rchar #replace by char
-        return text # leave as is
+            return rchar  # replace by char
+        return text  # leave as is
     return re.sub("&#?\w+;", fixup, text)
+